Hybrid Starter Drive Isolation via Flexible Torque Transfer
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Solution Overview
Problem
Conventional starter and ring gear systems in hybrid drive vehicles fail to withstand the higher number of starting cycles, leading to inadequate performance and increased manufacturing costs due to the need for stronger accessory drive belts and components, which also result in reduced fuel economy and comfort issues when accessories are not operational.
Innovation Solution
A starter and accessory drive system utilizing a drive pulley, starter motor, and flexible drive members to transfer torque from the starter motor to the engine crankshaft, allowing for efficient re-starting and independent operation of accessories, with a clutch mechanism to control torque transfer and disengage the starter motor once the engine is running.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the conventional starter motor and ring gear system is used to start the internal combustion engine in hybrid vehicles, then the starting function is achieved, but the system fails to withstand the much higher number of starter cycles (800,000 times) expected over the lifetime of a hybrid vehicle compared to conventional vehicles (50,000 times)
Solution Approach 1:
The patent extracts the starting function from the conventional starter motor and ring gear system, and implements it through the alternator/motor combined with the accessory drive belt system. This separates the high-cycle starting function from the components that would otherwise be subject to wear from repeated engagement and disengagement.
Solution Approach 2:
The alternator/motor is designed to serve dual functions: generating electrical power during engine operation and providing starting torque when needed. This multi-functionality eliminates the need for a dedicated starter motor designed for high-cycle operation, as the alternator can perform both roles.
2Reliability
If the alternator/motor is used to re-start the engine after short term shutdown, then the starter cycle reliability is improved, but the accessory drive belt must be much stronger and under higher tension to transmit the necessary torque (exceeding 140 Newton meters)
Solution Approach 1:
The patent changes the operational parameters of the accessory drive belt system by using it to transmit high torque for starting. This requires selecting belt materials and designs with higher strength characteristics, but allows the use of a lighter alternator/motor compared to a dedicated high-cycle starter motor.
Solution Approach 2:
The patent merges the starting function with the accessory drive belt system that already exists in the vehicle. By combining these functions, the system uses existing components (belt, tensioners, pulleys) for dual purposes, reducing overall system complexity despite the increased strength requirements of the belt.
3Power
If the accessory drive belt is tensioned higher to transmit starting torque, then the starting capability is achieved, but parasitic losses in the belt increase resulting in fuel economy decreases
Solution Approach 1:
The system dynamically adjusts belt tension requirements based on operational mode. During starting, high tension is required to transmit torque. During normal operation, the belt tension can be reduced since the alternator is generating power rather than receiving it for starting. This dynamic adjustment reduces average parasitic losses.
Solution Approach 2:
The high-tension starting mode operates periodically rather than continuously. The alternator/motor provides starting torque only when the engine needs restarting, while during normal operation the system operates in power generation mode with different tension characteristics. This periodic high-tension operation reduces cumulative energy losses.
4Adaptability or versatility
If the accessory drive is tensioned in one direction when the engine is running and in the other direction when the engine is being started by the alternator/motor, then the starting function is achieved, but the design requires special purpose idlers and/or tensioners and may require multiple instances, increasing manufacturing expense
Solution Approach 1:
The patent inverts the conventional starting approach by using the alternator/motor to drive the engine through the accessory belt system, rather than using a starter motor to directly crank the engine. This reversal enables the use of existing accessory drive components for starting purposes, though it does require modifications to handle bidirectional tensioning.
Solution Approach 2:
The accessory drive belt system acts as an intermediary between the alternator/motor and the engine crankshaft during starting. This intermediary role allows the use of standard belt-driven accessory components, though special purpose idlers and tensioners are needed to manage the bidirectional tensioning requirements.
5Loss of energy
If the internal combustion engine is stopped to improve fuel economy, then fuel consumption is reduced, but the accessory drive system is not operating causing reduced comfort level and unsafe operating conditions for accessories like power steering pump
Solution Approach 1:
The alternator/motor serves as a universal power source that can both restart the engine and directly drive accessories when the engine is stopped. This multi-functionality allows accessories to remain operational during engine stop events, maintaining comfort and safety while preserving fuel economy benefits.
Solution Approach 2:
The accessory drive belt system acts as an intermediary that can transmit power from the alternator/motor to accessories even when the engine is not running. This allows accessories to operate independently of engine operation status, maintaining functionality during fuel-saving stop events.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enhances the durability and efficiency of the starter system, reduces manufacturing costs, and maintains accessory operation even when the engine is stopped, improving fuel economy and occupant comfort by isolating the accessory drive from the engine crankshaft and using a dedicated drive motor for accessories.
Implementation Method 1
a second flexible drive member operable to transfer the torque produced by the starter motor to the drive pulley to re-start the engine
Implementation Method 2
a second flexible drive member operable to transfer the torque produced by the starter motor
Data Source
AI summary
A starter and accessory drive system and method for hybrid drive vehicles is provided. The invention isolates the accessory drive system from the transfer of torque between a starter motor and the crankshaft of the engine. In one embodiment, a dedicated flexible drive member transfers torque from the starter motor to the crankshaft to re-start the engine. In another embodiment, a torque transfer control is employed to selectively apply torque from the starter motor to the accessory drive, to drive the accessories when the engine is stopped, and/or to the engine crankshaft to re-start the engine. In another embodiment of the invention, the accessory drive is isolated from the engine crankshaft and is instead driven by a drive motor on the accessory drive while the engine crankshaft is connected to a starter motor and/or generator which can be energized to re-start the engine.